SMS05 through SMS24
PROTECTION PRODUCTS
Applications Information
Device Connection for Protection of Four Data Lines
SMSxx Circuit Diagram
The SMSxx is designed to protect up to four unidirec-
tional data lines. The device is connected as follows:
1. Unidirectional protection of four I/O lines is
achieved by connecting pins 1, 3, 4 and 6 to the
data lines. Pin 2 and 5 are connected to ground.
The ground connections should be made directly to
the ground plane for best results. The path length
is kept as short as possible to reduce the effects
of parasitic inductance in the board traces.
Circuit Board Layout Recommendations for Suppres-
sion of ESD
Protection of Four Unidirectional Lines
Good circuit board layout is critical for the suppression
of ESD induced transients. The following guidelines are
recommended:
z
z
z
z
Place the SMSxx near the input terminals or con-
nectors to restrict transient coupling.
Minimize the path length between the SMSxx and
the protected line.
Minimize all conductive loops including power and
ground loops.
The ESD transient return path to ground should be
kept as short as possible.
z
z
Never run critical signals near board edges.
Use ground planes whenever possible.
Matte Tin Lead Finish
Matte tin has become the industry standard lead-free
replacement for SnPb lead finishes. A matte tin finish
is composed of 100% tin solder with large grains.
Since the solder volume on the leads is small com-
pared to the solder paste volume that is placed on the
land pattern of the PCB, the reflow profile will be
determined by the requirements of the solder paste.
Therefore, these devices are compatible with both
lead-free and SnPb assembly techniques. In addition,
unlike other lead-free compositions, matte tin does not
have any added alloys that can cause degradation of
the solder joint.
www.semtech.com
2004 Semtech Corp.
5
SEMTECH [ SEMTECH CORPORATION ]
